The present invention relates to a desalinating apparatus using an absorption refrigerator which utilizes natural energy, a desalination system, a method of desalinating saline water, and a method of producing right of emitting carbon dioxide, and more particularly relates to a desalinating apparatus using an absorption refrigerator of open-regeneration type which utilizes dilute saline water and concentrated saline water, a desalination system, a desalinating method, and a method of producing right of emitting carbon dioxide.
In an arid region, a region where soil is deteriorated with salt, or a region where severe contamination of water takes place, supply of fresh water is an important issue, which can be utilized for household use, industrial use, agricultural use, improvement of soil properties, prevention of salt-precipitation in soil, or the like. In addition, regulation over carbon dioxide emission into the atmosphere with the consumption of fossil fuel is focused on in recent years, in connection with issues on the global greenhouse effect. Therefore, a transaction of a right of emitting carbon dioxide is also under consideration. In this context of the global greenhouse effect, there are attempts for removing carbon dioxide from the atmosphere through regeneration (recover) of vegetation in arid regions. When fresh water produced by a desalination process is utilized for this purpose, the subject is how to desalinate saline water using natural energy.
As background arts for desalinating saline water such as seawater, there are a multi-stage flash distillation method, a multi-effect distillation method, a reverse-osmosis method, an electrodialysis method, a vapor compression method, a freezing method, and so on. Even when the reverse-osmosis method is employed, which is considered to consume smaller amount of energy in desalinating seawater, electricity of 7kWh is practically consumed in producing 1 ton of fresh water. Therefore, a practice of such desalination is actually accompanied by a large amount of fossil fuel-consumption, which gives rise to problems from a point of view of costs, saving energy, reducing carbon dioxide emission, and so on.
Desalination which utilizes solar energy and which does not consume fossil fuel has been widely tried. For example, a system which produces fresh water by a reverse osmosis method utilizing electricity generated by a solar thermal generator or solar batteries and another system which produces fresh water by a distillation method which utilizes differential temperature of seawater or solar thermal energy have been studied. However, there are problems in costs. Although throughput of a multi-effect distillation method which utilizes solar thermal energy is of several 10 kg/day per unit area (1 square meter) of solar radiation, which is relatively large, the problem is that the costs of obtaining a durable structure against natural conditions such as a strong wind or an adhesion of sands are remarkably increased.
As a kind of heat-pump which is employed in an air-conditioning and heating system, absorption refrigerators are widely spread, which utilize thermal energy. As a heat source for these, solar thermal energy etc. other than the fossil fuel can be utilized. A type of absorption refrigerator having an open-regeneration field is known, which employs a solution of lithium bromide or calcium chloride and which utilizes solar thermal energy. This is a system suitable for arid regions. However, there are few studies on this absorption refrigerator for desalination. Furthermore, there are few studies on structure of a low-cost absorption refrigerator which is fit for desalination utilizing natural energy.
The present invention is made in view of the above-mentioned subjects, and an object of the present invention is to develop a novel fresh water resource therefor. Another object of the present invention is to provide a novel desalinating apparatus which utilizes natural energy. Yet another object of the present invention is to provide a novel desalination system which utilizes natural energy. Still another object of the present invention is to provide a novel method of desalinating saline water which utilizes natural energy. Still another object of the present invention is to provide a novel method of producing right of emitting carbon dioxide which contributes to control over atmospheric emission of carbon dioxide in desalinating saline water. Still another object of the present invention is to provide a novel method of producing right of emitting carbon dioxide, which stimulates fixation of carbon dioxide of atmosphere by means of vegetation which are produced through desalinated saline water. Accordingly, the above-mentioned objects and other related objects are achieved by the present invention disclosed herein.
Namely, a desalinating apparatus according to an embodiment of the present invention includes an absorption refrigerator which operates using concentrated saline water and first dilute saline water. The features are that second saline water for desalination is evaporated utilizing heat which flows out from a high-temperature heat source of the absorption refrigerator, and that fresh water is obtained through condensation of water vapor which has been evaporated from the second saline water utilizing heat which flows in a refrigeration source of the absorption refrigerator.
In the above desalinating apparatus, plural absorption refrigerators may be employed, which may be disposed in series in a serial arrangement.
A desalinating apparatus according to another embodiment of the present invention includes a plurality of absorption refrigerator units, each includes a refrigeration source plate having no water-permeability, a first dilute saline water holding member which is brought into close contact with a surface of the refrigeration source plate, a high-temperature heat source plate having no water-permeability, a concentrated saline water holding member which is brought into close contact with a surface of the high-temperature heat source plate and which is disposed opposite the first dilute saline water holding member, and a second dilute saline water holding member which is brought into close contact with another surface of the high-temperature heat source plate. Further, the plurality of absorption refrigerator units are aligned in series in a serial arrangement, wherein each second dilute saline water holding member is disposed opposite another surface of the adjacent refrigeration source plate.
In the above desalinating apparatus, each of the plurality of absorption refrigerator units may further include a fresh water holding member which is brought into close contact with another surface of the refrigeration source plate.
In the above desalinating apparatus, a plurality of gap-keeping members may further be provided for keeping within a prescribed range a gap between the first dilute saline water holding member and the concentrated saline water holding member and a gap between the second dilute saline water holding member and the refrigeration source plate.
In the above desalinating apparatus, the serial arrangement may be made along a closed line.
In the above desalinating apparatus, a vacuum system may further be provided, which includes a vacuum chamber in which a space including the plurality of absorption refrigerator units is evacuated so as to have substantially the same pressure.
A desalination system according to yet another embodiment of the present invention includes means for supplying first dilute saline water, means for supplying concentrated saline water, means for supplying second dilute saline water for desalination, an absorption refrigerator which utilizes the concentrated saline water and the first dilute saline water, means for evaporating the second dilute saline water, which utilizes heat flowing out from the high-temperature heat source of the absorption refrigerator, and means for collecting condensed fresh water, which condense the water vapor evaporated from the second dilute saline water utilizing heat flowing in the refrigeration source of the absorption refrigerator.
In the above desalination system, means for heating the concentrated saline water and means for heating the dilute saline water may further be provided. In this case, means for exchanging heat of water which flows in the absorption refrigerator for that of water which flows out therefrom.
In the above desalination system, a vacuum system which evacuates the absorption refrigerator may further be provided.
In the above desalination system, a salt-precipitation field which re-concentrate the concentrated saline water in which a salt-concentration thereof has been decreased.
A method of desalinating saline water using an absorption refrigerator according to still another embodiment of the present invention includes the steps of supplying first dilute saline water to a refrigeration source of the absorption refrigerator, supplying concentrated saline water in which molar salt-concentration thereof is higher than that of the first dilute saline water to a high-temperature heat source of the absorption refrigerator, supplying second dilute saline water for desalination to the absorption refrigerator, draining the first dilute saline water in which salt-concentration thereof has been increased due to evaporation of water, draining the concentrated saline water in which salt-concentration thereof has been decreased due to absorption of water, draining the second dilute saline water in which salt-concentration thereof has been increased due to evaporation of water, and collecting condensed fresh water. Features of the method of desalinating saline water are that the fresh water for desalination is produced through evaporation of the second dilute saline water using heat flowing out from the high-temperature heat source of the absorption refrigerator and through condensation of water vapor which has evaporated from the second dilute saline water using heat absorbed in the refrigeration source of the absorption refrigerator.
In the above desalinating method, the step of regenerating the concentrated saline water which re-evaporates water of the concentrated saline water in which concentration thereof has been decreased due to absorption of water may further be provided.
In the above desalinating method, the step of evacuating the absorption refrigerator may further be provided.
In the above desalinating method, the step of heating the first dilute saline water, the second dilute saline water, and the concentrated saline water supplied. In this case, the step of exchanging heat of the first dilute saline water, the second dilute saline water, and the concentrated saline water supplied for heat of the first dilute saline water, the second dilute saline water, the concentrated saline water exhausted, and the fresh water collected, may further be provided.
A method of producing right of emitting carbon dioxide is provided according to still another embodiment of the present invention. This substitutes a desalination system which emits a high amount of carbon dioxide to a desalination system which utilizes natural energy, and obtains a right of emitting carbon dioxide by operating the desalination system which utilizes natural energy according to the above-mentioned method of desalinating saline water.
A method of producing right of emitting carbon dioxide according to still another embodiment of the present invention may produce a right of emitting carbon dioxide through the step of fixing carbon dioxide of the atmosphere, wherein vegetation is grown using the fresh water which is produced as described above.